SignatureVerifier.sol

// SPDX-License-Identifier: MIT
pragma solidity 0.7.0;

contract SignatureVerifier {
  /**
   * @notice Recovers the address for an ECDSA signature and message hash, note that the hash is automatically prefixed with "\x19Ethereum Signed Message:\n32"
   * @return address The address that was used to sign the message
   */
  function recoverAddress (bytes32 hash, uint8 v, bytes32 r, bytes32 s) public pure returns (address) {
    bytes memory prefix = "\x19Ethereum Signed Message:\n32";
    bytes32 prefixedHash = keccak256(abi.encodePacked(prefix, hash));
    
    return ecrecover(prefixedHash, v, r, s);
  }
  
  /**
   * @notice Checks if the recovered address from an ECDSA signature is equal to the address `signer` provided.
   * @return valid Whether the provided address matches with the signature
   */
  function isValid (address signer, bytes32 hash, uint8 v, bytes32 r, bytes32 s) external pure returns (bool) {
    return recoverAddress(hash, v, r, s) == signer;
  }
}